The present invention relates to fasteners in general and, more in particular, to fasteners that use swagable collars to lock pins and collars together in fastening workpieces.
Fastener systems that use a pin and swagable collar have been known for a long time. In general, the pin of such a system has a head that bears on one side of two or more workpieces, a shank that extends through the workpieces, and annular or helical locking grooves on the side of the workpieces opposite the head. The pin may be further classified as a pull type or stump type. For the pull type, an installation tool swages the collar over the locking grooves while pulling on the pin so that collar material flows into the locking grooves to axially interfere with the pin and lock the pin, collar and workpieces together in a joint. While the installation tool pulls on the pin, it also forces the collar to bear against the workpieces to cooperate with the head in compressively loading the workpieces. The joint continues to enjoy this compressive load throughout its life. Except for the pulling on the pin, stump type pins are set the same way.
It has also been known for some time to use helically grooved or threaded pins with swaged collars to fasten workpiees together in the manner just described. Alternately, a standard nut and bolt fastener system can use the threaded pin as the bolt. The threaded pins used with a swaged collar or in a threaded fastener system makes the pin versatile.
The root of the helical groove between the flanks of the thread on the pin is a leak path whether the pin is used with a swaged collar or a threaded collar, and this has long been recognized as a disadvantage of a threaded pin. When swaged, the collar material does not reach to the root of the helical groove.